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中国长江流域典型区域地下水干旱预测研究

Groundwater Drought Prediction in the Typical Catchment of Yangtze River Basin in China

  • 摘要: 地下水干旱的发生会对地下水系统以及相关社会产业和生态系统造成不可忽视的危害,因此,准确预测地下水干旱的发生具有重要的现实意义。研究以我国长江流域中受人类影响较小的典型区域为例(湖南省和四川省),以天然净补给(Precipitation-EvapoTranspiration,P-ET)、土地利用与土地覆盖等地下水干旱的关键驱动因素为预测因子,结合门控循环单元(Gated Recurrent Unit,GRU)这一深度学习模型和支持向量机(Support Vector Machine,SVM)、多元线性回归(Multiple Linear Regression,MLR)等机器学习模型,通过预测研究区域基于GRACE(Gravity Recovery and Climate Experiment)反演的地下水储量变化(Ground Water Storage Anomaly,GWSA),进而计算基于GRACE的地下水干旱指数,从而预测地下水干旱。此外,研究就影响P-ET的气象变量是否适合作为输入变量也进行了探究。主要结论如下:(1)对于湖南省,MLR模型预测的GWSA预见期最长,SVM模型预见期最短。在预见期内,GRU预测效果最好,SVM预测效果最差。在输入变量选择方面,加入影响P-ET的气象变量提升了SVM和MLR模型对GWSA的预测性能,但降低了GRU模型的预测性能。在地下水干旱预测方面,MLR模型且输入变量中剔除影响P-ET的气象变量方案能更好的捕捉地下水干旱动态。(2)对于四川省,所有方案在检验期的GWSA预测值与参考值均较接近,除了前中期和末期未能预测到部分峰值。加入影响P-ET的气象变量使3种模型显示出更好的GWSA预测效果。在地下水干旱预测方面,采用SVM模型或MLR模型且输入变量中剔除影响P-ET的气象变量,取得了令人较满意的预测效果。

     

    Abstract: Groundwater drought could cause non-negligible harm to groundwater system, social industries and ecosystems which depend on groundwater. It is of great significance to accurately predict groundwater drought. As case studies in the typical regions with less human influence in Hunan Province and Sichuan Province in the Yangtze River Basin, groundwater droughts in typical regions are predicted by using the key influencing factors, such as natural net recharge(P-ET), landuse and landcover, as predictors of gated recurrent unit(GRU), which is a deep learning model, and support vector machine(SVM)/multiple linear regression(MLR), which are machine learning models, respectively. It adopts the groundwater storage anomaly(GWSA) derived from GRACE as the output of the models, and consequently calculates the groundwater drought index based on GRACE. In addition, this paper also explores whether meteorological variables affecting P-ET are suitable as input variables. The main conclusions are as follows:(1) In Hunan, a typical region in the Yangtze River Basin, the MLR has the longest forecast period of GWSA, and the forecast period of SVM is the shortest. During the forecast period, GRU has the best prediction performance and SVM has the worst prediction efficiency. In terms of input variable selection, adding meteorological variables that affect PET improves the prediction performance of SVM and MLR models for GWSA, but reduces the prediction performance of GRU model. In terms of groundwater drought prediction, the case in which the MLR model excludes meteorological variables affecting P-ET shows a better ability to capture groundwater drought dynamics.(2) In Sichuan, a typical region in the Yangtze River Basin, the predicted GWSA of all cases in the test period are close to the reference value, except for some peaks that cannot be caught in the middle and late stages. Adding meteorological variables affecting P-ET can improve the prediction performance of the three models for GWSA. In terms of groundwater drought prediction, using SVM model or MLR model and excluding meteorological variables affecting P-ET can achieve relatively satisfactory performance in groundwater drought prediction.

     

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